Balancing valve



I May 27,1947. 2,421,219

/ BALANCING VALVE Filed March 4, 1942 Snventor attorney Patented May 27, 1947 BALANCING VALVE Ralph E. Price, Highfield, Md., assignor to Landis Tool Company, Waynesboro, Pa.

Application March 4, 1942, Serial No. 433,365

This invention relates to hydraulic systems,

'particularly those wherein one or more of the hydraulically operated devices must be driven at a constant speed.

In hydraulic systems having a plurality of operated mechanisms supplied from a single source, the operation of a device such as a work rest, a foot-stock; or a chuck which occurs during the operation of continuously operated mechanisms requires a substantially constant pressure. The rate of movement of such a device is not important. Operation of these devices would cause a change in speed of another device in the same system whose function requires more or less continuous operation at a substantially constant speed, such as a traverse mechanism or a work drive mechanism. However, change in load on the constant speed mechanism will cause fluc tuation in pressure on the constant pressure device. This is just as objectionable as interference with the constant speed mechanism.

There are disclosed in the prior'art a few de- 2 than that for which the reliefvalve is set under that required for the other constant pressure mechanisms.

A further object is to provide a hydraulic system having both constant speed mechanisms and constant pressure mechanisms.

Figure 1 is a sectional elevation of a balancing valve shown in conjunction with a hydraulic systern having constant speed mechanisms and constant pressure mechanisms.

Figure 2 is a section on the line 22 of Figure 1.

' In the drawings, numeral I0 indicates a valve body, and l I a valve member sliclably mounted in Said valve is cylindrical in shape and divides the bore into two chambers l2 and I3. In one end of said valve are tangential" passages l4thru the wall of the cylinder. Said passages permit fluid under pressure to enter port vices whose purpose is to maintain a constant flow of fluid under pressure. This result is obtained solely by dividing the supply of fluid, di-,

recting part of it thru a restriction to the driven mechanism, and another part to the exhaust. The efiect of this is to maintain a balance of pres-' sure in the metering means of the fluid going to the driven mechanism and in that of the fluid to Y be bypassed. This type of system permits the use 7 of only one driven mechanism under the desired conditions such as constant speed or" constant pressure. The introduction of even one additional device would interfere with the desired functioning of the first. v

By dividing the output of a pump between the constant speed mechanism and the constant pressure mechanisms, and by providing a device to maintain a pressure in the supply line to the constant speed circuit equal to the pressure'in the constant pressure circuit, a constant'flow of fluid under, pressure" may be. maintained to the constant speed device so long as the pressure required therefor does not exceed that of the constant pressure circuit. Also, a constant force may be exerted in the operation of the-back rest, footstock, chuck or other constant pressure device.

It is therefore an object of my invention to provide a. hydraulic system wherein one or more mechanisms may be driven at a constant speed I5 from said valve and to pass from there thru passage Hi to constant speed motor l1. Another constant speed motor 19 receives through l8, fluid under pressure from valve which is identical with valve 10. Fluid is directed to said valve from line 2| thru line "33, restriction 36 and line 34.

The other end of valve 25 is connected to constant pressure line 21 thru line 31. Fluid under pressure for said system is supplied by a constant delivery pump 20 thru branch lines 2|, and 26 and lines 22 and 21 respectively to opposite ends of valve ll. Restrictions 23 and 24 in lines 2| and 22 respectively, are in the form of throttle valves although restriction 24 need not be adjustable.

' Constant pressure devices consisting ofvcylinders 28 and 30 and pistons 29,,and3l respectively therein are connected by lines 38 and 32 to line 21 between restriction 24 andvalve body 10. A valve 40 serves to connect cylinder 30 with pressure line 32 or exhaust line 4|, A relief valve 35 p is connected to the same portion of line 21.

, Operation Fluid under pressure from pump 20 passes thru restrictions and 24. The pressure exerted by the constant pressure portionof the circuit which is established byrelief valve 35 is imposed on the right end of valve II. The pressure in line 21 must be greater at all times than thepressure required to maintain a constant flow of fluid to motor I1. Since-chamber l2 of valve body I0 is regardless of the varying resistance of these 1 mechanisms. regardless of the viscosity of the fluid, and regardless of other mechanisms in the equal in area to chamber I3 of valve body 10, y it is obvious'that valve ll will assume a position in relation to port ii to maintain a pressure in, system so long as the pressure required is less chamber 12, equal to that in l3. It is also obmaintained equal to that in chamber 1 3 only by a flow thru valve 23 sumcient to maintain a pressure drop from line 2i to line 26 equal to that from line 22 to 21, and that in order for this flow to occur valve Ii must assume a position in relation to port litoallow just that amount of flow. Any more than sufiicient opening between valve H and port 15 would result in a greater pressure drop between lines 21 and 26 than between 22 and 21 which would result in more pressure in chamber l3 than chamber 12 which would tend to close the port is and thus increase pressure in chamber [2. Any less than suflicientopening be-- tween valve H and port would result in a less pressure drop between line 2! and '26 than between 22 and 21 which would result in less pressure in chamber 13 thanin chamber l2 which would tend to open port i 5 and decrease pressure-in line 26 until it is substantially the same as in line 21.. Thus with the pressure in line 26' maintained equal to the pressure in line .21, the pressure drop across the two valves 23 and'24 is maintained equal and the flow will be approximately proportional to the openingsjnthese restrictions. Any tendency to a drop in pressure in the system as a result of fluid used to shift pistons 29 and 3| would be transmitted thru valve II to effect a corresponding drop in pressure in line 26. There would be no change in the volumeof fiuid'supplied to motor I! because valve taining said constant pressure, means for supplying a constant volume ot-fluid under pressure to the constantspeed devices-including a branch from the pump output for the constant pressure devices' a separate branch for each constant speed device, a restricting means in each of said branches and means including a valve in the constant speed branch for maintaining pressure in the supply to the constant speed branch equal to that in the supply to the constant pressure branch.

2.,In a hydraulic system, a pump, a plurality .oi' hydraulically operated devices supplied from restriction in each division of said conduit for determining the volume of fluid for each device, a line connecting corresponding sides of said restrictions, a valve in said line including a housing a piston therein having equal areas at opposite ends thereof, the ends of said piston being subjected to the pressures existing at said corresponding sides of said valve, an'outlet from said Number Name Date 2,005,731 Ernst June 25, 1935 1,972,462 Schafer Sept. 4, 1934 2,102,865 Vickers Dec. 21, 1937 40 2,111,964 Crane Mar. 22, 1988 2,166,940 Conradson July 25, 1939 2,272,684 Vickers e.. Feb. 10, 1942 2,223,838 Tweedale Dec. 3, 1940 2,255,787 Kendrick Sept. 16, 1941 1,999,834

housing for supplying one of said constant speed REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Ernst Apr. 30, 1935 

